There's likely an underground stream in your city, but it may soon be seeing the light.

Uncovering buried streams has had huge impacts in places as diverse as Seattle, Washington, Kalamazoo, Michigan, and even Seoul, Korea—improving local water quality, providing habitat for fish and birds, and turning neglected parking lots and roads into public parks that boost neighbors' property values and can revitalize entire cities. And city planners everywhere are starting to take note.

In Yonkers, the fourth largest city in New York State, officials are a third done with a "daylighting" project—a term for the opening up of underground streams (see "11 Rivers Forced Underground"). In addition to exposing a waterway that had long been covered, the effort has already sparked plans for a new minor-league ballpark and new housing.

"I credit the city and the people who ... figured that having a nice river in a downtown was something that was, economically, really good," said Ann-Marie Mitroff, director of river programs for Groundwork Hudson Valley, an environmental justice nonprofit.

But why are all these streams covered at all? Flash back more than a hundred years. In many urban areas around the world, small streams were just getting in the way. You couldn't build on top of them, and the rapidly growing populations in many cities were throwing all their sewage into open water.

Often, engineers found that the simplest solution was to bury the streams, routing the water into pipes and paving over the top. In Yonkers, "the Army Corps of Engineers put a parking lot on top of it, which everybody thought was progress," Mitroff said. [Editor's note: A spokesperson for the U.S. Army Corps of Engineers says there are no records of the agency covering streams in Yonkers, and said the Corps would not have had jurisdiction to do so. They pointed to local authorities as most likely responsible; National Geographic has been unable to confirm that.]

In some cities, more than 70 percent of streams have been paved over. In many cases, city residents don't even know that there are buried waterways under their feet.

The Saw Mill River before it was uncovered, as it winds underground.

Photograph by Steve Duncan

Now, new research and a desire to revitalize urban cores is leading to a host of daylighting projects. Uncovering buried streams has been proposed in San Francisco, Baltimore, and Detroit, as well as in smaller urban areas nationwide.

Uncovering streams can help reduce flooding. When it rains in a "natural" watershed, soil and plants absorb the water. When it rains onto a parking lot that drains into an underground pipe, the potential for flooding is much larger.

According to a new report from advocacy nonprofit American Rivers, released July 17, urbanization increases the likelihood of floods getting worse. One study found that paving over 25 percent of a watershed could turn a formerly rare severe flood into a twice-a-decade event. When more than 65 percent of a watershed is paved over, those so-called "hundred-year-floods" could hit every year.

Watch the Money Flow

Early daylighting projects, like Arcadia Creek in Kalamazoo, focused on the economic benefits of bringing streams back to the surface. Turning a parking lot into a 3/4-mile-long (1.2-kilometer-long) strip of Arcadia Creek in downtown Kalamazoo created a park that hosts five annual festivals and generates $12 million in annual tourism dollars.

But Arcadia Creek isn't really a creek. According to a report from the Virginia Tech Water Resources Research Center, the Arcadia Creek project and similar ones do "not resemble streams per se, but rather canals with surrounding parkland ... [the streams] are very controlled water channels [with] concrete-lined basins."

In Seoul, a $384 million project daylighted three miles (five kilometers) of stream that has most of its water pumped in from a river seven miles (11 kilometers) away. Both parks have been successful in boosting the economic value of the surrounding land and bringing locals a little closer to nature.

Digging up a stream isn't cheap. In Hutchinson, a town in rural Kansas, daylighting just three city blocks of Cow Creek cost more than $4 million, including relocating four buildings out of the new floodplain. But compared to the cost of unearthing, replacing, and reburying the city's aging pipes, building a new downtown park was an easy choice.

Not all daylighting projects need to be the centerpiece of an urban revitalization project. In Washington, D.C., the District Department of the Environment (DDOE) is undertaking small daylighting projects of a few hundred feet (around a hundred meters) in upper Northwest D.C., which is more suburban than urban, despite its location within the nation's capital.

Each project will create a small amenity for immediate neighbors, but they are mostly intended to mitigate local flooding and improve water quality. "Water in a pipe is not exposed to biological processes that break down pollution," said Steve Saari, watershed protection specialist with DDOE.

A recent EPA study found that streams exposed to sunlight are up to 23 times more efficient at processing nitrogen, which left unprocessed can cause dead zones where fish cannot survive.

Return of a "Living Stream"

In Yonkers, the uncovered stream is "a living stream," Mitroff says.

The first reopened part of the stream (which opened in 2012) is already filled with fish and "fairly good-size" American eels, up to 18 inches (46 centimeters) long. "It's remarkable," Mitroff said.

In D.C., only months after daylighting a tributary to Rock Creek, "we've seen a lot more birds, and a lot more unusual birds," said Saari.

For the lovers of rivers, discover the hidden ones. They are local to mountains higher than 1500 meter above sea level. Their water comes from deep sea level, gets heated by earth core heat, turns to vapor, ascends up, and condenses within cold mountain heights. They are the secret of caves and ground tunnels. They open at sea, tens of meters below sea level. Good luck. (check: http://www.salmanalkasimi.com/researches/First_Research.pdf)

This is what we can do in Fort Bragg California. Two year 'round creeks flow beneath our town and continue through culverts across the Noyo Headlands (the former G-P mill site). We could open these up and restore them from Hy#1 out to the Pacific.

Its a great idea to resurface once forgotten streams and creeks, because
I have yet to visit a community that doesn't have at least one buried
waterway. I am a firm believer that by improving our surface waters on
land that we may be able to control the nutrient runoff going into our
oceans and creating dead zones.

this really does make a once ugly urbanized city have that little bit of how its suppose to look feel im from kalamazoo and the arcadia creek area is sweet the summer time is great down there even if it is concrete basin as mentioned above a so called canal it still makes a beatiful spot in downtown kalamazoo i love my city

this really does make a once ugly urbanized city have that little bit of how its suppose to look feel im from kalamazoo and the arcadia creek area is sweet the summer time is great down there even if it is concrete basin as mentioned above a so called canal it still makes a beatiful spot in downtown kalamazoo i love my city

Excellent. I live in a relatively small town that has rivers that disappear under streets and reappear again miles later. It's fascinating to ponder just how many streams are under our streets. It's time they've resurfaced!

"The Nature Of Cities" follows the journey
of Professor Timothy Beatley as he explores urban projects around the
world, representing the new green movement that hopes to move our urban
environments beyond sustainability to a regenerative way of living.

I viewed your 39 minute documentary and really related to your theme. Have you viewed "Lost Rivers" (2011) a 70 minute documentary that includes the Saw Mill River Daylighting in Yonkers, NY. I was in charge of the project and I also appear several times in the film. Would suggest you get a look at it produced by Catbird Productions Katarina Soukoup, Montreal Canada. I took hundreds of progress photos from beginning to end including the underground chambers and screeninc systems that will never be seen again.